Wireless signal



March 22, 193.2.v R HERZOG '1,850,548

WIRELESS SIGNAL Filed Jan. l2, 1929 inw/M014:

Patented Mar. 22, 1932 UNITED STATES PATENT carica ROBERT HERZOG, OFBERLIN, GERINIANY, ASSIGNOR TO C. LORENZ AKTIENGESELL- SCHAFT, OFBERLIN-TEMPELHOF, GERMANY WIRELESS SIGNAL Application led Januaryiif,L1929, Serial No. 332,186, and in Germany January 81, 1928.

In the United States application of Fel-iX Gerth and Fritz Gutsmann,Serial No. 156,095, filed December 21, 1926, Pat. Nq 1,800,996, a wayhas been given for removing, in alternating current circuits especiallyin the oscillation circuits for wireless transmitters, undesireddisturbing waves such as, for instance, occur in the form of disturbingside waves with frequency 'multiplica-tion by means of static frequencytransformers.

Figures 1 and 2 are curves explanatory of my invention, and

Figure 3 shows a preferred embodiment of my invention.

Absorption circuits were mentioned there, which have the property ofabsorbing definite, particularly disturbing frequencies which are oftenvery near the useful wave; for 1nstance when the 9th harmonic of aparticular fundamental frequency is to be used as the utility wave, toabsorb the 7th and 11th harmonic. They have, on the other hand, in theirentirety the character of a rejector circuit, that is to say, a highresistance for the utility wave. Tn Fig. 1 is shownthe curve of theapparent resistance of such an arrangement for all frequencies. For thesake of greater clearness the frequency itself is not represented as theabscissa, but the proportion X of any desired frequency o to a forinstance, to the utilized frequency (on). Frequencies that are less thanthe normal frequency o0 are represented by the value X and frequenciesgreater than @o are represented by so that the axis of the abscissatakes a finite value with the value wo, that is X=1 in the centre. Theapparent resistance R is represented as ordinate, which becomesinfinitely great at on, on the other hand, at w1 the lower lyingdisturbing secondary waves) and at m2 (the upper lying disturbing waves)equal to O. F or infinitely great and infinitely small frequencies theresistance R increases again t0 This arrangement according to theapplication Ser. No. 156,095 has,

actually, in relaparticular frequency tion to other well-known iiltercircuits a particularly good absorbing action in the sense mentioned.Nothing has been said, however, about the best dimensions of theindividual circuits, that is to say, the ratio or the damping. This isalso unnecessary here where it is a matter of not allowing a main waveto go through, and for given secondary waves, to create a short-circuitthrough an absorption circuit for each. For this reason, self-inductioncoils and capacities in the same order of magnitude as the remainingcircuit elements of the transmitter were hitherto chosen. If still morethan two secondary waves were present the same number of absorptioncircuits had to be provided as the number of disturbing waves.

The present invention hasfor its objectto remove disturbing waves evenstill further away (for instance w3, or and o5, Fig. 1) with only twoabsorption circuits which are tuned to two specially disturbingsecondary Waves.y

This lis done not only by satisfying the resonance conditions given insaid application Ser. N o. 156,095 (for instance, with two disturbingwaves three resonance conditions) but also, by giving the resonancecurve of the yresistance sucha form, that also frequencies still furtheraway nd a very small resistance, while the three other conditions, thegreatest possible resistance for the utility wave, andthe smallestpossible resistance (shortcircuit) for the two most disturbing secondarywaves, remain satisfied the same as before. Such a form of the resonancecurve can, be attained by giving to the capacit-ies eX- tremely largevalues and the self-induction coils extremely small values, that is tosay, by making the ratio obtained. Further it is to be observed that Yi, Further it it ybeing of circuit;

the damping of the arrangement is made as little as possible, in ordernot to remove the advantage of the widened range of small resistance, byflattening the resonance curve at the point wg, or by increasing theresistance at (1)1 (1)2. Y f Y Forinstance, the self-induction coilsGand 8 consists each of a single t-urn or even less than a completeturn, of a conductor which, in'order to vproduce the'smallest ydamping`possible, comprises a plural-ity of strands o high frequency wire, oflarge cross :section, connected in parallel. To satisfy the resonanceconditions, the condensersmust.l be `of correspondingly high values, forinstance 3 toV 4^ mfs, with a utilizedwave of =50O m.,

likewise important that the condensers should; have the smallestpossible resistance losses. e

As can be seen from the curve in Fig-2 the oscillation resistance R islikewise small for frequencies, which lie rather far above and below theutilized frequency while the value of R at no `increases very quickly toa high value, y Therefore the entire frequency band is almost completelysuppressed, on one sidel between the perpendiculars I and III and on'the other side between II and IV, and it must alsoy be taken intoconsideration that normally the amplitudes of the disturbing frequenciesconstantly decreasewith the distancefrom m0. Y i

Y is advantageous to connect the absorption circuit arrangement to suchlaces of the utility oscillation circuit, where, for lthe futility, wavethe smallest differences ofpotential prevail. vFig. showsfthis `form Inthis circuit l is a frequency` transformer which besides the utilizedwave Vcomprises awholey Yspectrum 'of secondary waves, two krof whichare usually particularly strongly pronounced andl lierather neartheutilized; wave.- The circuit 15,213 4 is tuned to the utilized wave.Ifthe capacities 2 and 3 are correctly 'chosen in relation to the selfinduction coils 'l and 4l, then on the points A and B, there prevailsfor the utilized' wave, a potential node,'that is to say, these are twopoints of the smallest difference of potentialfor the utility wave whilefor all other frequencies a more or less great capacitive or inductivepotential'ispresent. The combination of filter and rejector circuit 6, 78,l 9 is connected tok these points A and B. The resistance ofr thiscombination is very highv for the utility wave, 1 for both the adjacentside waves practically 0, andv is for those waves still further away,which get weaker and weaker, the lfarther they are from the utilizedfrequency, still very low so that in the circuit 6, 7, a current flowsofy the frebination of a circuit containing capacity and inductancetunedto a signalling frequency, a circuit arrangement bridged acrosssaid tuned circuit and having two parallel conf nected paths eachcontaining serially related capa-city. and ind-uctance, one path beingtuned to a frequency below and ,the other to a frequency above thesignalling frequency, and the lcapacities and inductances of said pathsbeing 4so relatedthat'said circuit arrangement oers -very low,approximately uniform, impedance to bands of frequencies 'both 'aboveand below the signalling frequency, and very high impedance yto the signalling frequency.

Ina wireless signalling system, the combination offtwo connectedcircuits,each containing capacity and yinduct-ance and tuned to aysignalling frequency, a circuit interf posed between said firstmentioned circuits and `having two parallel connected paths cachcontaining serially related capacity and induct-ance, one ypath beingtuned to a frequency below and the'other to a frequency above thesigna-lling frequency, and the capacities and inductanceS .0f Saidpaths-being so related that said interposed circuit-offers very low,approximatelyuniform, impedance to a band of frequencies above andto abandy of fre-V quencesk below the signalling frequency, and

veryy high impedance to the signalling frequency. Y i 1 In testimonywhereof I have alixed my signature. 'c

i ROBERT HERZOG.

Y quency ofthe utilized wave and practicallyY y

